- Email: [email protected]
Impact of Intensive Greenhouse Production System on Soil Quality
Pedosphere 25(2): 282–293, 2015 ISSN 1002-0160/CN 32-1315/P c 2015 Soil Science Society of China ° Published by Elsevier B.V. and Science Press
Impact of Intensive Greenhouse Production System on Soil Quality 1∗
2
1
1
1
Tarek G. AMMARI , , Ragheb TAHHAN , Nizar AL SULEBI , Alaedeen TAHBOUB , Rakad A. TA’ANY and Samih ABUBAKER3 1 Departemnet
of Water Resources and Environmental Management, Faculty of Agricultural Technology, Al-Balqa’ Applied University, Al-Salt 19117 (Jordan) 2 Departement of Natural Resources and Environment, Faculty of Agriculture, Jordan University of Science and Technology, Irbid 22110 (Jordan) 3 Department of Plant Production and Protection, Faculty of Agricultural Technology, Al-Balqa’ Applied University, Al-Salt 19117 (Jordan) (Received May 10, 2014; revised January 9, 2015)
ABSTRACT Composite top- and subsoil samples were collected from the greenhouses in the Al-Balawneh area, Jordan, where intensive greenhouse production system (IGPS) has been practiced since 1998, to study the impact of IGPS on soil quality as measured by the chemical and biological properties to develop a sustainable production system. The study showed that IGPS led to higher electrical conductivity in top- and subsoils compared to an uncultivated soil (control). Quality and amount of irrigation water, lack of efficient drainage, and quantity and types of applied fertilizers were major factors resulting in salt buildup. IGPS resulted in lower total N (TN) and NO3 -N in the soil compared to the control. The lower TN was due to crop uptake, microbial immobilization, volatilization, and irregular application of composted animal manure or poultry manure. In contrast, higher residual Olsen-P content was detected in both soil layers of greenhouses than in the control. Residual P was classified as very high in the topsoil layers and sufficient to high in the subsoil layers. Residual available K in the soils of greenhouses was relatively lower than that in the control and it was, however, classified as high to very high. A large increase of Cl and a considerable decrease in the bacterial count were observed in both soil layers of IGPS compared to the control treatment. Economically sustainable soil management practices need to be adopted by farmers to achieve a sustainable and profitable production. This can be accomplished through education, targeted towards the farming community in the central Jordan Valley. Key Words:
central Jordan Valley, salt buildup, soil health, soil management, unsustainable agriculture practices
Citation: Ammari, T. G., Tahhan, R., Al Sulebi, N., Tahboub, A., Ta’any, R. A. and Abubaker, S. 2015. Impact of intensive greenhouse production system on soil quality. Pedosphere. 25(2): 282–293.
INTRODUCTION The unsustainable agricultural practices during the last few decades are the main causes for environmental degradation in the West Asia and North Africa regions, including Jordan, especially through their impacts on soil and water resources. Consequently, there is an increasing interest in sustainable and environmental friendly intensive greenhouse production systems that optimize yields while sustain soil, fauna, water and energy, and protect the environment. Jordan Valley is the most potential agriculture area in Jordan, where a variety of long-term intensive greenhouse agricultural activities (i.e., irrigation, fertilization, etc.) are undertaken. The area supplies food and cash crops such as vegetables (tomato, pepper and others), fruits, and bananas. Up to now, the sustainability of such activities is not yet assessed. To enforce sustainable agricultural ∗ Corresponding
author. E-mail: [email protected].
development and to collect essential environmental information, a regional chemical and biological survey of soils should be conducted in the Jordan Valley. Data from such regional survey can play an important role in evaluating the impact of long-term intensive greenhouse production practices on soil quality, i.e., soil fertility and soil chemical and biological properties. The major objective of soil quality/fertility assessment is to predict, from the knowledge of soil properties, the ability of the soil to support specific functions for the crop, animals-humans, and water target systems (Harris and Bezdicek, 1994). It could be also used as a management tool to help farmers to select specific management practices (e.g., fertilization) and as a measure of sustainability (Doran and Parkin, 1994). Most recently, Hu et al. (2012) reported that an investigation of the actual status of soil fertility in the intensive greenhouses could enable stakeholders to develop fu-
PRODUCTION SYSTEM IMPACT ON SOIL QUALITY
ture strategies for nutrient management and sustainable agriculture through saving inputs and preventing environmental damages resulting from nutrient losses. Local field observations suggest that many production systems are fertilized in excess; i.e., fertilizers are applied in excess of plant demands for optimum yield, without any criteria that allows for a rational use of mineral as well as organic fertilizers. In fact, diagnostic tools of soil nutrients and nutritional status of growing crops are often disregarded, since few growers perform soil and/or leaf analysis on a regular basis. This might be due to farmers’ perception that an increase in fertilization always results in a yield increase. However, an excess of, for example, N may cause environmental degradation (Gim´enez et al., 2001). According to Weinbaum et al. (1992), over-fertilization seems to be a common practice because of the failure to consider non-fertilizer sources of plant available N and conduct annual diagnosis of the N status in addition to the insensitivity of leaf N to over-fertilization. Indeed, nutrients added by irrigation water, released from organic matter and/or crop residues mixed with soils, and residual amounts of nutrients (from previous seasons) are neither quantified nor considered by many growers including those of the Jordan Valley. Therefore, to ensure adequate returns on agricultural investment (i.e., reducing the per-unit production costs), cost-effective utilization of fertilizers should be accomplished. The impacts of intensive greenhouse agricultural activities on the quality of the soil and water resources of a region should be studied in combination with the characteristics and particularities of the area in which these activities take place. Especially in the Jordan Valley region, the soil quality/fertility assessment is a difficult task. The area is characterized by high soil and climate diversity which results in a large number of management practices in a constricted area. Accordingly, this study was conducted in 2012 in Al-Balawneh area of the central Jordan Valley where intensive agricultural activities were practiced since 1998. To our knowledge, the long-term impact of intensive greenhouse production practices on soil chemical and biological properties in the central Jordan Valley has not been assessed yet. Thus, the main objectives of this study were: i) to determine the residual nutrient pool in soils and soil chemical and biological properties under the conditions of intensive tomato and pepper greenhouse production systems, ii) to investigate the impact of intensive greenhouse production system (IGPS) on soil quality/fertility, and iii) to suggest sustainable and environmental friendly greenhouse management practices. Such information
283
could play a future strategic role in soil nutrient management planning decisions. MATERIALS AND METHODS Study area The Jordan Valley, the main agricultural region in Jordan, is characterized by an arid Mediterranean, very warm bioclimate. This area has a mean maximum temperature varying between 22 and 40 ◦ C during summer months due to different altitudes (AlZu’bi and Al-Kharabsheh, 2003). The month of July is the hottest and January is the coldest during which the mean temperature drops to a minimum of 7 ◦ C. The mean annual precipitation ranges between 250 and 300 mm, which is typical for arid regions. The maximum reference evapotranspiration is 205.7 mm during July, while the minimum is 72.4 mm during January. Water consumption in the valley ranges from 2 000 to 8 000 m3 ha−1 season−1 . Reclaimed wastewater from the As-Samra Wastewater Treatment Plant was supplied to the central part of the Jordan Valley. On its course to the Jordan Valley it was diluted by surface runoff water from adjacent catchment areas and temporarily stored in the King Talal Reservoir. Although diluted, this reclaimed water contained nutrients and some salts, heavy metals and microbial contaminants. This irrigation water was classified as Class B water with a salinity range of 0.45– 2.00 g L−1 (FAO, 1993). The pH values, CaCO3 content, and organic matter content of the soils in the Jordan Valley ranged from 7.1 to 8.7, 100 to 650 g kg−1 , and 3 to 48 g kg−1 , respectively, in the topsoil (0–20 cm) and from 7.3 to 8.5, 50 to 700 g kg−1 , and 3 to 35 g kg−1 , respectively, in the subsoil (20–40 cm). Composted animal manure (mixtures of different ratios of poultry, sheep and cow manures) was applied annually and mixed with the upper 20 cm soil layer before growing crops in the Jordan Valley, particularly in greenhouses, with the amount of 10 to 20 t ha−1 year−1 (Ammari et al., 2013). Agricultural practices Soil samples were collected from the Al-Balawneh area (central Jordan Valley). The agricultural practices at the study site represented typical management of crops and soils under greenhouse conditions in the central Jordan Valley. Intensive greenhouse production system has been practiced at the study site since 1998, where greenhouses (500 m2 each) were cultivated with tomato and pepper crops. Crops were irrigated with the water from King Abdullah Canal till 2009 and alte-
284
T. G. AMMARI et al.
rnatively from the King Abdullah Canal and King Talal Reservoir since 2009. The agricultural practices of IGPS are summarized as follows: 1) removal of crop residues, plastic sheets, weeds, etc.; 2) 30 cm deep tillage; 3) soil sterilization; 4) composted animal manure application at a rate of 500 kg per greenhouse, with organic matter (OM) of 500–600 g kg−1 , N content of 12–18 g kg−1 , C:N ratio of 11.2–15.2, and pH value of 6.8–7.5; 5) installation of plastic sheets; 6) installation of drip irrigation tubes, with 5 furrows spaced 80 cm apart in each greenhouse and two irrigation pipes for each furrow; 7) installation of plastic mulch on furrows; 8) operation of irrigation system for 10 continuous hours followed by transplanting; and 9) irrigation and fertilization (Table I). Soil sampling and analyses Soil samples were collected in early June, about one month after last application of fertilizers, from the greenhouses few weeks before the succeeding production cycle. Top- (0–20 cm) and subsoil (20–40 cm) samples were collected from the greenhouses and prepared for analysis. To substantially represent uniform field areas that have a similar crop, fertilizer, soil management, and irrigation history and to improve the quality of sampling to better reflect the average status of soil quality, forty two composite soil samples were prepared for analysis. Composite samples consisted of one hundred and twenty six subsamples: sixty and fifty four subsamples were collected from randomly distributed greenhouses being cultivated with pepper and tomato, respectively, and twelve soil subsamples were taken from random locations of uncultivated soil. Soil samples were air-dried, crushed, and ground to pass through a 2-mm sieve. For biological analyses, separate samples of about 100 g each, taken from the same soil sampling locations, were packed on ice and shipped for immediate analysis.
Some chemical parameters were analyzed: pH, electrical conductivity (EC), total N (TN), NO3 -N, OlsenP (plant available P), available K (soluble and exchangeable fractions extracted with ammonium acetate), soluble Na, Ca, Mg, and Cl (extracted with deionized water), SO4 , OM, and CaCO3 . Chemical analysis was carried out on 1:1 (w:v) soil:water extracts according to Ryan et al. (2001). Total N was determined by digestion, distillation and titration. Available K and soluble Na in the extract were determined by flame photometer. Soluble Ca and Mg, soluble Cl, OM, and CaCO3 were determined by titration with ethylenediaminetetraacetic acid, AgNO3 , ferrous ammonium sulfate, and NaOH, respectively. NO3 -N in the extract was analyzed by ultraviolet spectrophotometric screening method. SO4 was extracted with calcium chloride dihydrate. Olsen-P was extracted by 0.5 mol L−1 NaHCO3 (adjusted to pH 8.5) and determined by spectrophotometer according to Ryan et al. (2001). Microbial counts (bacteria, fungi, and actinomycetes) were determined by the standard plate count method according to Zuberer (1994). Statistical analysis The results of the chemical and biological analyses were discussed in reference to those of uncultivated soil collected from the same study site and the critical levels established by research in other areas with approximately similar conditions. To establish if there are significant differences among the treatments for different measured parameters, the t-test (two-tailed distribution, two-sample unequal variance) was used at P ≤ 0.01. RESULTS Soil pH and electrical conductivity The average soil pH values in the topsoil were 8.0
TABLE I Fertilization schedule for tomato and pepper plants cultivated in the central Jordan Valley in 2007–2012 Crop
Fertilizer type
Application time
Application rate
Tomato
12:61:0a) 20:20:20 15:15:30 Humic acid + 15:15:30 12:12:36 + 12:12:44 (liquid) 40:0:0 20:20:20 Ca-containing fertilizer 10:17:27 10:12:36
1 week after transplanting 1 month later 1 month later Later At harvesting From transplanting till ripening From transplanting till ripening From transplanting till ripening At ripening Last 2 weeks
2 2 2 1 2 3 3 3 3 3
Pepper
a) N:P:K.
kg per greenhouse (GH), once a week for 4 weeks kg per GH, once a week for 4 weeks kg per GH, once a week for 8 weeks L + 1 kg per GH, once a week for 1 month kg + 1 L per GH, once a week till end of season kg per GH, 4 times every 2 weeks kg per GH, once every 4 d for 1 month kg per GH, twice a month kg per GH, once every 4 d for 1 month kg per GH, once every 4 d
PRODUCTION SYSTEM IMPACT ON SOIL QUALITY
and 8.2, respectively, for the pepper and tomato greenhouses, whereas the uncultivated soil had an average pH value of 8.1 in the topsoil (Fig. 1). Almost similar pH values were found in the subsoil layer. In contrast to soil pH, there were greater variations among the EC values (Fig. 1). The EC values in the topsoil were 3.01 and 2.97 dS m−1 for the tomato and pepper greenhouses, respectively, compared to 1.18 dS m−1 in the uncultivated soil. Salt accumulation was also observed in the subsoil where the tomato and pepper greenhouses had EC values of 2.04 and 2.61 dS m−1 , respectively, compared to 0.71 dS m−1 in the uncultivated soil. Soil TN and NO3 -N The contents of TN and NO3 -N in the intensively managed greenhouses and uncultivated soil in both soil layers are shown in Fig. 2. TN in the topsoil ranged from 0.6 to 1 g kg−1 , however, the subsoil of pepper greenhouses had 1.6 g kg−1 TN compared to 0.4 and 0.9 g kg−1 , respectively, for the tomato greenhouses and uncultivated soil (Fig. 2). In the current study, IGPS resulted in significantly higher residual NO3 -N contents for both soil layers compared to the uncultivated soil, particularly in the case of tomato greenhouses (Fig. 2). The residual soil NO3 -N after harvest was approximately 7.4, 4.1 and 2.5 mg kg−1 , respec-
285
tively, for the tomato greenhouses, pepper greenhouses and uncultivated soil in the topsoil layer (Fig. 2). Soil NO3 -N also accumulated in the subsoil layer (4.7, 3.5, and 1.3 mg kg−1 , respectively, for the tomato greenhouses, pepper greenhouses and uncultivated soil). Soil Olsen-P There was significantly higher Olsen-P content in the greenhouse soils than in the uncultivated soil in both soil layers (Fig. 3). In the uncultivated soil, OlsenP content was 39.1 and 22.8 mg kg−1 , respectively, for the top- and subsoils. In the tomato greenhouses, it was 135.2 and 81.3 mg kg−1 for the top- and subsoils, while in the pepper greenhouses the corresponding values were 139.4 and 84.8 mg kg−1 , respectively. Available K, soluble Ca and Mg, and OM The values of soil fertility indicators such as available K (soluble and exchangeable K) in the topsoil layer of greenhouses were significantly lower than those in the uncultivated soil (Fig. 4). IGPS, particularly in the case of pepper, led to a significant increase (P < 0.05) in Ca content in both soil layers for both crops compared to that in the uncultivated soil (Fig. 4). IGPS also led to a significant increase (P < 0.05) in the Mg content for both crops compared to that in the uncultivated soil for both soil layers (Fig. 4).
Fig. 1 Soil pH and electrical conductivity (EC), with the extract ratio of 1:1 soil:water, in the top- (0–20 cm) and subsoil (20–40 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 18, 20, and 4, respectively, for tomato, pepper, and control).
286
T. G. AMMARI et al.
Fig. 2 Total N and NO3 -N in the top- (0–20 cm) and subsoil (20–40 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter(s) are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 18, 20, and 4, respectively, for tomato, pepper, and control).
Fig. 3 Olsen-P in the top- (0–20 cm) and subsoil (20–40 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 18, 20, and 4, respectively, for tomato, pepper, and control).
Only slight accumulation of organic matter was found in the soils of greenhouses compared to the uncultivated soil (Fig. 5). Soluble Na, soluble Cl, and SO4 IGPS resulted in much higher soluble Na, soluble Cl and SO4 concentrations in the soils of greenhouses compared to those in the uncultivated soil in both soil layers (Fig. 6). Compared with the tomato greenhouse production system, intensive pepper greenhouse production system resulted in even higher Cl concentra-
tion in the subsoil and higher SO4 concentration in both soil layers. Soil biological properties IGPS had an apparent impact on soil biological properties in the topsoils (Figs. 7 and 8). Microbial counts in the uncultivated soil followed a normal trend where bacteria dominated the numbers of microorganisms followed by actinomycetes and fungi. However, IGPS resulted in a significant decrease in the bacterial count compared to the uncultivated soil (Fig. 7) and a
PRODUCTION SYSTEM IMPACT ON SOIL QUALITY
287
Fig. 4 Available K and soluble Ca and Mg in the top- (0–20 cm) and subsoil (20–40 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter(s) are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 18, 20, and 4, respectively, for tomato, pepper, and control).
Fig. 5 Organic matter in the top- (0–20 cm) and subsoil (20–40 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 18, 20, and 4, respectively, for tomato, pepper, and control).
significant increase in the fungi/bacteria ratio (f/b) (Fig. 8). In addition, the intensive tomato greenhouse production system caused an increase in the fungal as well as actinomycetes counts compared to the pepper production system and the uncultivated soil (Fig. 7). DISCUSSION Soil pH and EC The soils of the study site are highly buffered due to their high CaCO3 content (430–500 g kg−1 ). The pre-
sence of CaCO3 buffers the soils in the pH of 7.5–8.5. Thus, the long-term annual application of composted animal manure is not expected to impact soil pH of these highly calcareous soils (Fig. 1). On the other hand, IGPS, including frequent composted animal manure application, continuous fertigation without soil leaching and efficient drainage of excess salts, and high evaporation conditions, resulted in significantly higher EC for both soil layers compared to those of the uncultivated soil (Fig. 1). Salt accumulation in the topsoil of the greenhouses was due to the upward movement of
288
T. G. AMMARI et al.
Fig. 6 Soluble Na, soluble Cl and SO4 in the top- (0–20 cm) and subsoil (20–40 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 18, 20, and 4, respectively, for tomato, pepper, and control).
soil water as evapotranspiration exceeded water application (irrigation). According to Rhoades et al. (1992), the EC threshold of tomato crop is 0.9 dS m−1 and Maas and Hoffman (1977) suggested that the threshold values were 1.5 and 2.5 dS m−1 , respectively, for pepper and tomato with 14.0% and 9.9% reduction in yield per unit increase in EC beyond the threshold. Consequently, progressive salt accumulation would have adverse impact on the yield of crop, particularly for pepper. Chen et al. (2004) evaluated soil fertility in vegetable production under the open-field and greenhouse conditions including intensive fertilizer use and irrigation and reported that soil EC was 0.44 and 0.35 dS m−1 for 0–5 and 5–10 cm soil depth, respectively, for the greenhouses of 1–5 years of vegetable production and 0.56 and 0.43 dS m−1 correspondingly for the 16– 20-year greenhouses. The observed differences of the
results between the current study and those of Chen et al. (2004) are attributed to the differences in climatic conditions, crop type, soil type (e.g., texture), quality and amount of irrigation water, quantity and types of applied fertilizers, and other agricultural and/or soil management practices (e.g., type and amount of applied organic materials and excess salt leaching and drainage). Soil TN and NO3 -N Although Chen et al. (2004) showed that the values of TN in surface soil layers (pH1:5 = 7.45–8.34) were higher in the greenhouses that had been in use for a longer period of time (1.00, 1.21, 1.43, and 1.90 g kg−1 for 1–5, 5–10, 11–15, and 16–20 years of greenhouse vegetable cultivation, respectively), IGPS under the conditions of the current study did not significantly
PRODUCTION SYSTEM IMPACT ON SOIL QUALITY
Fig. 7 Average bacterial, actinomycetes and fungal counts in the topsoil (0–20 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). CFU = colony forming unit. Bars with the same letter(s) within each microbial group are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 2, 9, and 10, respectively, for control, tomato, and pepper).
Fig. 8 Fungal/bacterial (f/b) ratio in the topsoil (0–20 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 9, 10, and 2, respectively, for tomato, pepper, and control).
influence TN particularly in topsoil layer in comparison with the uncultivated soil (Fig. 2). Diacono and Montemurro (2010) reported that repeated application of composted materials in semi-arid Mediterranean regions enhanced soil organic N content by up to 90%. Such finding was not supported by our study. Defoer et al. (2000) reported that low values of TN were found in organic plots, which could be the result of crop uptake and N loss through volatilization. Current finding is in agreement with the latter one. Other factors might include irregular application of composted animal manure and/or poultry manure, which are rapidly decomposed leading to earlier N depletion. However, IGPS
289
of pepper crop significantly increased TN in the topsoil compared to that of tomato crop (Fig. 2). This might be attributed to the fact that farmers at the site of the current study annually applied mineral N at approximately 150 and 350 kg ha−1 , respectively, for tomato and pepper. In the subsoil layer, the TN of the uncultivated soil was even higher than that of the tomato IGPS (Fig. 2), which can be due to the growth of wild weeds with different root depths on the uncultivated soil. IGPS resulted in significantly higher residual NO3 N content for both soil layers compared to the uncultivated soil, particularly in the case of tomato greenhouses (Fig. 2). Nitrate uptake of pepper plants seemed to be much higher than that of tomato plants, which is in agreement with Yu et al. (2010), who reported that N uptake of tomato and pepper crops was 0.31 and 0.58 kg per 100 kg yield, respectively. The amounts of residual NO3 -N reported by this study (Fig. 2) are much lower than those reported in the literature. Hu et al. (2012) reported that soil residual NO3 -N after harvest was approximately 190–404 kg ha−1 at 0–60 cm soil depth in the greenhouses cultivated with vegetable crops. The differences could be attributed to the factors such as determination time of soil NO3 -N, annual N inputs from mineral fertilizers, type of N mineral fertilizer, application method of N fertilizer, timing of application, amounts of applied manures and their C:N ratios, cultivations of crops, and irrigation water in addition to the factors affecting gaseous losses of N. Several reports have shown that annual application of N to greenhouse vegetable crops has reached more than 1 000 kg ha−1 (Chen et al., 2004; Ju et al., 2009) in comparison to only 150 to 350 kg ha−1 in the current study. Moreover, the soil was graded based on its nutritional status for vegetable cultivation according to Shen and Zou (2004) and Alpaslan et al. (2005). Accordingly, residual TN as well as NO3 -N belonged to very low to medium and very low, respectively. This is in agreement with the fact that about 95% of TN in surface soils is organic N (Havlin et al., 2004). It can be concluded that TN in the soils might not be enough to support good plant growth in upcoming seasons or microbial activities and, therefore, supplementary N application is necessary under the conditions of the current study. Soil Olsen-P Significantly higher Olsen-P was found in the soils of greenhouses than in the uncultivated soil for both soil layers (Fig. 3), which can be attributed to the fact
290
that P was applied to the tomato and pepper greenhouses at high rates of approximately 234 and 192 kg P2 O5 ha−1 year−1 , respectively. The P accumulation in the IGPS may have consequently resulted from farmers’ excessive application of organic manure and compound fertilizers to obtain higher yields without any pre-plant-soil test. Previous studies have shown that long periods of greenhouse cropping caused soil available P enrichment in greenhouses (Chen et al., 2004; Yang et al., 2010), which was confirmed by our study. Chen et al. (2004) showed that available P in the soil surface layers was higher in the greenhouses used for a longer period of time (117, 158, 118, 257 mg kg−1 Olsen-P for 1–5, 5–10, 11–15, 16–20 years of greenhouse vegetable cultivation, respectively), fertilized with mineral and organic P at a rate of 410 and 565 kg ha−1 , respectively, for tomato and sweet pepper. Soil P accumulation under IGPS suggests that there is a need of better nutrient management for IGPS. In the agricultural areas with intensive farming practices, excessive application of P has led to increasing P concentrations in soils, increasing the risk of P losses by runoff, erosion and subsurface drainage water (Stanley et al., 1995). In addition, the excessive available P in soils may lead to micronutrient deficiency (e.g., Zn deficiency). According to Alpaslan et al. (2005), the residual Olsen-P in this study was classified as very high in topsoil layer and sufficient to high in subsoil layer for the tomato and pepper greenhouses. Moreover, Dobermann and Fairhurst (2000) stated that soil P in most cultivated soils was higher than the critical level of 25 mg kg−1 in calcareous soils and the differences could be explained by the application rates of fertilizer at different locations. Our results indicated that farmers at the study site did not consider soil available P status before application of additional fertilizer. Yu et al. (2010) reported that the overdose of fertilizer applied in greenhouses led the amount of available P in soil far beyond the required. In the greenhouse soils, the amount of available P was 135–377 mg kg−1 , while its required level for vegetables was only 60–90 mg kg−1 . However, soil P readily reacts with calcium ions, clay minerals and organic components in soils to form relatively insoluble substances. Similar to soil NO3 , inorganic P is also negatively charged in most soils. Dissimilarly, P does not behave like NO3 because of its reactivity with other soil constituents. Available K, soluble Ca and Mg, and OM Available K in all soil samples including the uncultivated soil was classified as high to very high in
T. G. AMMARI et al.
both soil layers according to Alpaslan et al. (2005), although available K in the topsoil under IGPS was lower than that in the uncultivated soil (Fig. 4). The results of this study are higher than those reported in the literature. Yu et al. (2010) reported available K in greenhouse soils of 192 to 764 mg kg−1 . Similarly, Chen et al. (2004) reported available K in greenhouse soils of 67 to 753 mg kg−1 and that tomato and sweet pepper were fertilized with mineral and organic K at a rate of 232 and 283 kg ha−1 , respectively. In the current study, tomato and pepper were fertilized with mineral K at a rate of approximately 240 kg ha−1 . Similar to P, farmers at the study site should also consider the residual available K in soils when applying K fertilizers to succeeding crops. Intensive greenhouse production led to a significant increase in Ca in top- and subsoils for both crops, particularly in the case of pepper. Significant increase in Mg content was also found in both soil layers for both crops compared to that in the uncultivated soil (Fig. 4). The observed increases in Ca and Mg can be partially attributed to greater dissolution of CaCO3 /MgCO3 due to higher partial pressure of carbon dioxide (PCO2 ) in the cultivated soils. In the subsoil, significantly higher Ca and Mg contents in the case of pepper might be attributed to the differences in root architecture (e.g., root depth) and consequently PCO2 of subsoil. No considerable accumulation of organic matter (OM) was found in the soils of greenhouses compared to the uncultivated soil (Fig. 5), which can be attributed to the fact that the temperature of greenhouses is much higher and the activity of microorganisms is stronger resulting in rapid mineralization of applied organic materials (Yu et al., 2010). Coskan et al. (2012) also reported that about 30% and 50% of the surveyed greenhouses had soil OM content of 10– 20 and 20–30 g kg−1 , respectively. Soluble Na, soluble Cl, and SO4 Intensive greenhouse production led to significant accumulation of Na, Cl, and SO4 in both soil layers, particularly in the case of pepper (Fig. 6). Because Cl is usually supplied to plants from various sources, particularly from irrigation water (maximum concentrations of total dissolved solids, Cl, and Na in the water of the King Talal Reservoir were 2 595, 532.5, and 345 mg L−1 , respectively) (Ammari et al., 2013), there is much more concern about its toxic levels in plants than deficiency. The Cl concentration in the external solutions of more than 710 mg L−1 can lead to Cl toxicity in sensitive plant species (Marschner, 1986). High Cl concentrations might have more detrimental effect on
PRODUCTION SYSTEM IMPACT ON SOIL QUALITY
pepper than on tomato plants, which can withstand Cl concentration up to approximately 1 380 mg L−1 . In the semiarid and arid regions, the Na concentration of approximately 1 150 to 2 300 mg L−1 is typical under irrigation and have a rather detrimental effect on the growth of most crop plants (Marschner, 1986). Although accumulation of soluble Na was found under the conditions of IGPS compared to the uncultivated soil, Na concentration was far below that reported by Marschner (1986). The SO4 concentration of 3 to 5 mg L−1 in solution is sufficient for most crops (Havlin et al., 2004). Large seasonal and year-to-year fluctuations in SO4 can occur due to the influence of environmental conditions on organic S mineralization, downward or upward movement of SO4 in soil water, and SO4 uptake by plants. The SO4 content in soils is also affected by the application of S-containing fertilizers and irrigation water. High concentrations of Cl and SO4 might affect soil quality. Therefore, leaching and drainage practices should be reconsidered for intensive greenhouse production practices. Soil biological properties Agricultural practices such as cropping index (i.e., percentage of the number of crops grown on a given land area per year), irrigation and water quality, type, timing and rate of fertilizers, and plant protection measures at the study site had adverse effects on soil EC, Na, Cl, SO4 , and NO3 contents, which might explain the variations in soil biological properties (i.e., bacterial counts and fungi:bacteria ratio) in comparison with those of the uncultivated soil (Figs. 7 and 8). In the case of tomato greenhouse production system, the observed significant increase in fungal counts, compared to those of pepper greenhouse production system and uncultivated soil (Fig. 7), might be an indication of the quality of soil OM, i.e., an increase in lignin and humus fractions. Fungal growth increases when the lignin fraction of soil OM increases since fungi are more adapted to lignin decomposition compared with bacteria. Sources of plant nutrients (synthetically derived minerals vs. decomposed organic material) have larger effect on microbial communities than land management systems (organic, low-input, or conventional) (Bossio et al., 1998). A different soil microbial community was reported by long-term organic fertilization experiments (Toyota and Kuninaga, 2006; Chu et al., 2007; Espersch¨ utz et al., 2007). Such variations of soil biological properties result from the nature of the added organic amendment, where complex compounds favor the growth of fungi and actinomycetes, and partly, because of the addition of the manure-
291
associated microorganisms in large numbers (Green et al., 2007). Espersch¨ utz et al. (2007) reported low f/b values of 0.017 and 0.024 for mineral and organic fertilizer amendments, respectively. Generally, the f/b ratio increased with higher amount of fertilizer added, suggesting that enhanced nutrient availability supported fungal growth. However, this contradicts other studies reporting high soil fertility and nutrient availability to favor bacteria over fungi (Grayston et al., 2001). It is likely that the changes in microbial communities cannot be solely attributed to quantitative differences in resource supply. Besides fertilizer regime, the identity of crop species also influenced microorganisms (i.e., actinomycetes counts under tomato and pepper intensive greenhouse systems) as shown in Fig. 7 and as found by Ngosong et al. (2010). The disproportionate response of microorganisms could be derived from plant specific differences in rhizo-deposition or root architecture since they can affect the ratio of microbial carbon to organic carbon (Anderson and Domsch, 1989; Insam et al., 1989). Overall, the impact of crop type on soil microorganisms was more pronounced than long-term fertilizer practice. This underlines the fact that root exudation and root morphology actively shaped soil microbial communities (Berg and Smalla, 2009). Moreover, management practices like the timing of fertilizer and manure applications can interact with crop biological factors, i.e., root architecture and exudates. Thus, the observed response of microorganisms to both crops (Fig. 7) was basically an overall effect of all factors linked with crops. This is essential for the achievement of sustainable agriculture and soil conservation, since crop rotation does not only affect the related plant symbionts but also selects the associated microorganisms, which in turn fulfill important functions for plant growth, soil health and quality (Wu et al., 2008). CONCLUSIONS The IGPS with excess fertigation but poor drainage under high evaporation conditions resulted in higher EC in top- and subsoils compared to the uncultivated soil. Progressive salt accumulation was expected to have adverse impact on yield of particularly pepper. IGPS under the conditions of this study also resulted in low soil N. Low TN was probably due to crop uptake, loss through volatilization and irregular application of composted animal manure or poultry manure. Much higher Olsen-P contents in the soils of greenhouses, compared to that in the uncultivated soil, were due
292
to the excessive application of animal manure, mineral P and compound fertilizers to obtain high yields. The Olsen-P was categorized as very high in the topsoil layer and sufficient to high in the subsoil layer, which poses environment risks. Available K in the topsoil layer of greenhouses was relatively lower than that in the uncultivated soil. However, the available K in all soil samples including the uncultivated soil was considered to be high to very high in both soil layers. IGPS did not influence soil OM content but increased Na, Cl and SO4 concentrations in both soil layers compared to the uncultivated soil. Progressive Cl accumulation is expected to have adverse effect on yield of particularly pepper crop. IGPS caused a considerable decrease in the bacterial count compared to the uncultivated soil. Although not significant, the intensive tomato greenhouse production system caused an increase in the fungal and actinomycetes counts compared to both pepper IGPS and uncultivated soil. It can be concluded that not only the intensive production practices but also crop types had an impact on soil biological properties. Current findings suggest that sustainable and profitable soil management practices should be adopted by farmers in the central Jordan Valley through targeted extension programs to educate farmers on the best management practices. ACKNOWLEDGEMENT Authors would like to thank the Jordan Valley Authority for their technical and laboratory assistance. REFERENCES Alpaslan, M., Gunes, A. and Inal, A. 2005. Research Techniques. AU Agriculture Faculty Publish, Ankara. Al-Zu’bi, Y. and Al-Kharabsheh, A. 2003. Multicriteria analysis for water productivity in the Jordan Valley. Int. Water Resour. As. 28: 501–511. Ammari, T. G., Tahhan, R., Abubaker, S., Al-Zu’bi, Y., Tahboub, T., Ta’any, R., Abu-Romman, S., Al-Manaseer, N. and Stietiya, M. H. 2013. Soil salinity changes in the Jordan Valley potentially threaten sustainable irrigated agriculture. Pedosphere. 23: 376–384. Anderson, T. H. and Domsch, K. H. 1989. Ratios of microbial biomass carbon to total organic carbon in arable soils. Soil Biol. Biochem. 21: 471–479. Berg, G. and Smalla, K. 2009. Plant species and soil type cooperatively shape the structure and function of the microbial communities in the rhizosphere. FEMS Microbiol. Ecol. 68: 1–13. Bossio, D. A., Scow, K. M., Gunapala, N. and Graham, K. J. 1998. Determinants of soil microbial communities: Effects of agricultural management, season, and soil type on phospholipids fatty acid profiles. Microbial Ecol. 36: 1–12. Chen, Q., Zhang, X. S., Zhang, H. Y., Christie, P., Li, X. L., Horlacker, D. and Liebig, H. P. 2004. Evaluation of current
T. G. AMMARI et al.
fertilizer practice and soil fertility in vegetable production in the Beijing region. Nutr. Cycl. Agroecosys. 69: 51–58. Chu, H. Y., Lin, X. G., Fujii, T., Morimoto, S., Yagi, K., Hu, J. L. and Zhang, J. B. 2007. Soil microbial biomass, dehydrogenase activity, bacterial community structure in response to long-term fertilizer management. Soil Biol. Biochem. 39: 2971–2976. Coskan, A., Atilgan, A., Oz, H. and Isler, E. 2012. Instantaneous evaluation of nitrate, ammonium, phosphorus and potassium pools in greenhouse soils in Antalya Province of Turkey. Afr. J. Agr. Res. 7: 937–942. Defoer, T., Budelman, A., Toulmin, C. and Carter, S. E. 2000. Building common knowledge: Participatory learning and action research (Part 1). In Defoer, T. and Budelman, A. (eds.) Managing Soil Fertility in the Tropics. A Resource Guide for Participatory Learning and Action Research. Royal Tropical Institute, Amsterdam. pp. 165–166. Diacono, M. and Montemurro, F. 2010. Long-term effects of organic amendments on soil fertility. A review. Agron. Sust. Dev. 30: 401–422. Dobermann, A. and Fairhurst, T. H. 2000. Rice: Nutrient Disorders and Nutrient Management. Potash & Phosphate Institute, Potash & Phosphate Institute of Canada, and International Rice Research Institute, Singapore, Makati. Doran, J. W. and Parkin, T. B. 1994. Defining and assessing soil quality. In Doran, J. W., Coleman, D. C., Bezdicek, D. F. and Stewart, B. A. (eds.) Defining Soil Quality for a Sustainable Environment. SSSA Special Publication No. 35. Soil Science Society of America and American Society of Argonomy, Madison, WI. pp. 3–21. Espersch¨ utz, J., Gattinger, A., M¨ ader, P., Schloter, M. and Fließbach, A. 2007. Response of soil microbial biomass and community structures to conventional and organic farming systems under identical crop rotations. FEMS Microbiol. Ecol. 61: 26–37. Food and Agriculture Organization (FAO). 1993. The State of Food and Agriculture 1993. FAO, Rome. Gim´ enez, C., D´ıaz, E., Rosado, F., Garc´ıa-Ferrer, A., S´ anchez, M., Parra, M. A., D´ıaz, M. and Pe˜ na, P. 2001. Characterization of current management practices with high risk of nitrate contamination in agricultural areas of southern Spain. Acta Hortic. 563: 73–80. Grayston, S. J., Griffith, G. S., Mawdsley, J. L., Campbell, C. D. and Bardgett, R. D. 2001. Accounting for variability in soil microbial communities of temperate upland grassland ecosystems. Soil Biol. Biochem. 33: 533–551. Green, S. J., Michel Jr., F. C., Hadar, Y. and Minz, D. 2007. Contrasting patterns of seed and root colonization by bacteria from the genus Chryseobacterium and from the family Oxalobacteraceae. ISME J. 1: 291–299. Harris, R. F. and Bezdicek, D. F. 1994. Descriptive aspects of soil quality/health. In Doran, J. W., Coleman, D. C., Bezdicek, D. F. and Stewart, B. A. (eds.) Defining Soil Quality for a Sustainable Environment. SSSA Special Publication No. 35. Soil Science Society of America and American Society of Argonomy, Madison, WI. pp. 23–35. Havlin, J. L., Tisdale, S. L., Nelson, W. L. and Beaton, J. D. 2004. Soil Fertility and Fertilizers: An Introduction to Nutrient Management. 7th Edition. Pearson Prentice Hall, Upper Saddle River, NJ. Hu, Y. C., Song, Z. W., Lu, W. L., Poschenrieder, C. and Schmidhalter, U. 2012. Current soil nutrient status of intensively managed greenhouses. Pedosphere. 22: 825–833. Insam, H., Parkinson, D. and Domsch, K. H. 1989. Influence of macroclimate on soil microbial biomass. Soil Biol. Biochem.
PRODUCTION SYSTEM IMPACT ON SOIL QUALITY
21: 211–221. Ju, X. T., Xing, G. X., Chen, X. P., Zhang, S. L., Zhang, L. J., Liu, X. J., Cui, Z. L., Yin, B., Christie, P., Zhu, Z. L. and Zhang, F. S. 2009. Reducing environmental risk by improving N management in intensive Chinese agricultural systems. P. Natl. Acad. Sci. USA. 106: 3041–3046. Maas, E. V. and Hoffman, G. J. 1977. Crop salt tolerance— current assessment. J. Irr. Drain. Div. 103: 115–134. Marschner, H. 1986. Mineral Nutrition of Higher Plants. Academic Press, London. Ngosong, C., Jarosch, M., Raupp, J., Neumann, E. and Ruess, L. 2010. The impact of farming practice on soil microorganisms and arbuscular mycorrhizal fungi: Crop type versus long-term mineral and organic fertilization. Appl. Soil Ecol. 46: 134–142. Rhoades, J. D., Kandiah, A. and Mashali, A. M. 1992. The Use of Saline Waters for Crop Production. Irrigation and Drainage Paper No. 48. FAO, Rome. Ryan, J., Estefan, G. and Rashid, A. 2001. Soil and Plant Analysis Laboratory Manual. 2nd Edition. The International Center for Agricultural Research in the Dry Areas (ICARDA) and the National Agricultural Research Center (NARC), Aleppo, Syria. Shen, H. and Zou, G. Y. 2004. Parameters selection for evaluation of vegetable soil quality and its gradation. Chin. J. Soil Sci. (in Chinese). 35: 553–557.
293
Stanley, C. D., McNeal, B. L., Gilreath, P. R., Creighton, J. F., Graham, W. D. and Alverio, G. 1995. Nutrient-loss trends for vegetable and citrus fields in west-central Florida: II. Phosphate. J. Environ. Qual. 24: 101–106. Toyota, K. and Kuninaga, S. 2006. Comparison of soil microbial community between soils amended with or without farmyard manure. Appl. Soil Ecol. 33: 39–48. Weinbaum, S. A., Scott Johnson, R. and DeJong, T. M. 1992. Causes and consequences of overfertilization in orchards. HortTechnology. 2: 112–121. Wu, T., Chellemi, D. O., Graham, J. H., Martin, K. J. and Rosskopf, E. N. 2008. Comparison of soil bacterial communities under diverse agricultural land management and crop production practices. Microbial Ecol. 55: 293–310. Yang, L. J., Li, T. L., Li, F. S. and Lemcoff, J. H. 2010. Longterm fertilization effect on fraction and distribution of soil phosphorus in a plastic-film house in China. Commun. Soil Sci. Plan. 42: 1–12. Yu, H. Y., Li, T. X. and Zhang, X. Z. 2010. Nutrient budget and soil nutrient status in greenhouse system. Agr. Sci. China. 9: 871–879. Zuberer, D. A. 1994. Recovery and enumeration of viable bacteria. In Weaver, R. W., Angle, J. S. and Bottomley, P. S. (eds.) Methods of Soil Analysis. Part 2. Microbiological and Biochemical Properties. Soil Science Society of America, Madison, WI. pp. 119–144.
Impact of Intensive Greenhouse Production System on Soil Quality 1∗
2
1
1
1
Tarek G. AMMARI , , Ragheb TAHHAN , Nizar AL SULEBI , Alaedeen TAHBOUB , Rakad A. TA’ANY and Samih ABUBAKER3 1 Departemnet
of Water Resources and Environmental Management, Faculty of Agricultural Technology, Al-Balqa’ Applied University, Al-Salt 19117 (Jordan) 2 Departement of Natural Resources and Environment, Faculty of Agriculture, Jordan University of Science and Technology, Irbid 22110 (Jordan) 3 Department of Plant Production and Protection, Faculty of Agricultural Technology, Al-Balqa’ Applied University, Al-Salt 19117 (Jordan) (Received May 10, 2014; revised January 9, 2015)
ABSTRACT Composite top- and subsoil samples were collected from the greenhouses in the Al-Balawneh area, Jordan, where intensive greenhouse production system (IGPS) has been practiced since 1998, to study the impact of IGPS on soil quality as measured by the chemical and biological properties to develop a sustainable production system. The study showed that IGPS led to higher electrical conductivity in top- and subsoils compared to an uncultivated soil (control). Quality and amount of irrigation water, lack of efficient drainage, and quantity and types of applied fertilizers were major factors resulting in salt buildup. IGPS resulted in lower total N (TN) and NO3 -N in the soil compared to the control. The lower TN was due to crop uptake, microbial immobilization, volatilization, and irregular application of composted animal manure or poultry manure. In contrast, higher residual Olsen-P content was detected in both soil layers of greenhouses than in the control. Residual P was classified as very high in the topsoil layers and sufficient to high in the subsoil layers. Residual available K in the soils of greenhouses was relatively lower than that in the control and it was, however, classified as high to very high. A large increase of Cl and a considerable decrease in the bacterial count were observed in both soil layers of IGPS compared to the control treatment. Economically sustainable soil management practices need to be adopted by farmers to achieve a sustainable and profitable production. This can be accomplished through education, targeted towards the farming community in the central Jordan Valley. Key Words:
central Jordan Valley, salt buildup, soil health, soil management, unsustainable agriculture practices
Citation: Ammari, T. G., Tahhan, R., Al Sulebi, N., Tahboub, A., Ta’any, R. A. and Abubaker, S. 2015. Impact of intensive greenhouse production system on soil quality. Pedosphere. 25(2): 282–293.
INTRODUCTION The unsustainable agricultural practices during the last few decades are the main causes for environmental degradation in the West Asia and North Africa regions, including Jordan, especially through their impacts on soil and water resources. Consequently, there is an increasing interest in sustainable and environmental friendly intensive greenhouse production systems that optimize yields while sustain soil, fauna, water and energy, and protect the environment. Jordan Valley is the most potential agriculture area in Jordan, where a variety of long-term intensive greenhouse agricultural activities (i.e., irrigation, fertilization, etc.) are undertaken. The area supplies food and cash crops such as vegetables (tomato, pepper and others), fruits, and bananas. Up to now, the sustainability of such activities is not yet assessed. To enforce sustainable agricultural ∗ Corresponding
author. E-mail: [email protected].
development and to collect essential environmental information, a regional chemical and biological survey of soils should be conducted in the Jordan Valley. Data from such regional survey can play an important role in evaluating the impact of long-term intensive greenhouse production practices on soil quality, i.e., soil fertility and soil chemical and biological properties. The major objective of soil quality/fertility assessment is to predict, from the knowledge of soil properties, the ability of the soil to support specific functions for the crop, animals-humans, and water target systems (Harris and Bezdicek, 1994). It could be also used as a management tool to help farmers to select specific management practices (e.g., fertilization) and as a measure of sustainability (Doran and Parkin, 1994). Most recently, Hu et al. (2012) reported that an investigation of the actual status of soil fertility in the intensive greenhouses could enable stakeholders to develop fu-
PRODUCTION SYSTEM IMPACT ON SOIL QUALITY
ture strategies for nutrient management and sustainable agriculture through saving inputs and preventing environmental damages resulting from nutrient losses. Local field observations suggest that many production systems are fertilized in excess; i.e., fertilizers are applied in excess of plant demands for optimum yield, without any criteria that allows for a rational use of mineral as well as organic fertilizers. In fact, diagnostic tools of soil nutrients and nutritional status of growing crops are often disregarded, since few growers perform soil and/or leaf analysis on a regular basis. This might be due to farmers’ perception that an increase in fertilization always results in a yield increase. However, an excess of, for example, N may cause environmental degradation (Gim´enez et al., 2001). According to Weinbaum et al. (1992), over-fertilization seems to be a common practice because of the failure to consider non-fertilizer sources of plant available N and conduct annual diagnosis of the N status in addition to the insensitivity of leaf N to over-fertilization. Indeed, nutrients added by irrigation water, released from organic matter and/or crop residues mixed with soils, and residual amounts of nutrients (from previous seasons) are neither quantified nor considered by many growers including those of the Jordan Valley. Therefore, to ensure adequate returns on agricultural investment (i.e., reducing the per-unit production costs), cost-effective utilization of fertilizers should be accomplished. The impacts of intensive greenhouse agricultural activities on the quality of the soil and water resources of a region should be studied in combination with the characteristics and particularities of the area in which these activities take place. Especially in the Jordan Valley region, the soil quality/fertility assessment is a difficult task. The area is characterized by high soil and climate diversity which results in a large number of management practices in a constricted area. Accordingly, this study was conducted in 2012 in Al-Balawneh area of the central Jordan Valley where intensive agricultural activities were practiced since 1998. To our knowledge, the long-term impact of intensive greenhouse production practices on soil chemical and biological properties in the central Jordan Valley has not been assessed yet. Thus, the main objectives of this study were: i) to determine the residual nutrient pool in soils and soil chemical and biological properties under the conditions of intensive tomato and pepper greenhouse production systems, ii) to investigate the impact of intensive greenhouse production system (IGPS) on soil quality/fertility, and iii) to suggest sustainable and environmental friendly greenhouse management practices. Such information
283
could play a future strategic role in soil nutrient management planning decisions. MATERIALS AND METHODS Study area The Jordan Valley, the main agricultural region in Jordan, is characterized by an arid Mediterranean, very warm bioclimate. This area has a mean maximum temperature varying between 22 and 40 ◦ C during summer months due to different altitudes (AlZu’bi and Al-Kharabsheh, 2003). The month of July is the hottest and January is the coldest during which the mean temperature drops to a minimum of 7 ◦ C. The mean annual precipitation ranges between 250 and 300 mm, which is typical for arid regions. The maximum reference evapotranspiration is 205.7 mm during July, while the minimum is 72.4 mm during January. Water consumption in the valley ranges from 2 000 to 8 000 m3 ha−1 season−1 . Reclaimed wastewater from the As-Samra Wastewater Treatment Plant was supplied to the central part of the Jordan Valley. On its course to the Jordan Valley it was diluted by surface runoff water from adjacent catchment areas and temporarily stored in the King Talal Reservoir. Although diluted, this reclaimed water contained nutrients and some salts, heavy metals and microbial contaminants. This irrigation water was classified as Class B water with a salinity range of 0.45– 2.00 g L−1 (FAO, 1993). The pH values, CaCO3 content, and organic matter content of the soils in the Jordan Valley ranged from 7.1 to 8.7, 100 to 650 g kg−1 , and 3 to 48 g kg−1 , respectively, in the topsoil (0–20 cm) and from 7.3 to 8.5, 50 to 700 g kg−1 , and 3 to 35 g kg−1 , respectively, in the subsoil (20–40 cm). Composted animal manure (mixtures of different ratios of poultry, sheep and cow manures) was applied annually and mixed with the upper 20 cm soil layer before growing crops in the Jordan Valley, particularly in greenhouses, with the amount of 10 to 20 t ha−1 year−1 (Ammari et al., 2013). Agricultural practices Soil samples were collected from the Al-Balawneh area (central Jordan Valley). The agricultural practices at the study site represented typical management of crops and soils under greenhouse conditions in the central Jordan Valley. Intensive greenhouse production system has been practiced at the study site since 1998, where greenhouses (500 m2 each) were cultivated with tomato and pepper crops. Crops were irrigated with the water from King Abdullah Canal till 2009 and alte-
284
T. G. AMMARI et al.
rnatively from the King Abdullah Canal and King Talal Reservoir since 2009. The agricultural practices of IGPS are summarized as follows: 1) removal of crop residues, plastic sheets, weeds, etc.; 2) 30 cm deep tillage; 3) soil sterilization; 4) composted animal manure application at a rate of 500 kg per greenhouse, with organic matter (OM) of 500–600 g kg−1 , N content of 12–18 g kg−1 , C:N ratio of 11.2–15.2, and pH value of 6.8–7.5; 5) installation of plastic sheets; 6) installation of drip irrigation tubes, with 5 furrows spaced 80 cm apart in each greenhouse and two irrigation pipes for each furrow; 7) installation of plastic mulch on furrows; 8) operation of irrigation system for 10 continuous hours followed by transplanting; and 9) irrigation and fertilization (Table I). Soil sampling and analyses Soil samples were collected in early June, about one month after last application of fertilizers, from the greenhouses few weeks before the succeeding production cycle. Top- (0–20 cm) and subsoil (20–40 cm) samples were collected from the greenhouses and prepared for analysis. To substantially represent uniform field areas that have a similar crop, fertilizer, soil management, and irrigation history and to improve the quality of sampling to better reflect the average status of soil quality, forty two composite soil samples were prepared for analysis. Composite samples consisted of one hundred and twenty six subsamples: sixty and fifty four subsamples were collected from randomly distributed greenhouses being cultivated with pepper and tomato, respectively, and twelve soil subsamples were taken from random locations of uncultivated soil. Soil samples were air-dried, crushed, and ground to pass through a 2-mm sieve. For biological analyses, separate samples of about 100 g each, taken from the same soil sampling locations, were packed on ice and shipped for immediate analysis.
Some chemical parameters were analyzed: pH, electrical conductivity (EC), total N (TN), NO3 -N, OlsenP (plant available P), available K (soluble and exchangeable fractions extracted with ammonium acetate), soluble Na, Ca, Mg, and Cl (extracted with deionized water), SO4 , OM, and CaCO3 . Chemical analysis was carried out on 1:1 (w:v) soil:water extracts according to Ryan et al. (2001). Total N was determined by digestion, distillation and titration. Available K and soluble Na in the extract were determined by flame photometer. Soluble Ca and Mg, soluble Cl, OM, and CaCO3 were determined by titration with ethylenediaminetetraacetic acid, AgNO3 , ferrous ammonium sulfate, and NaOH, respectively. NO3 -N in the extract was analyzed by ultraviolet spectrophotometric screening method. SO4 was extracted with calcium chloride dihydrate. Olsen-P was extracted by 0.5 mol L−1 NaHCO3 (adjusted to pH 8.5) and determined by spectrophotometer according to Ryan et al. (2001). Microbial counts (bacteria, fungi, and actinomycetes) were determined by the standard plate count method according to Zuberer (1994). Statistical analysis The results of the chemical and biological analyses were discussed in reference to those of uncultivated soil collected from the same study site and the critical levels established by research in other areas with approximately similar conditions. To establish if there are significant differences among the treatments for different measured parameters, the t-test (two-tailed distribution, two-sample unequal variance) was used at P ≤ 0.01. RESULTS Soil pH and electrical conductivity The average soil pH values in the topsoil were 8.0
TABLE I Fertilization schedule for tomato and pepper plants cultivated in the central Jordan Valley in 2007–2012 Crop
Fertilizer type
Application time
Application rate
Tomato
12:61:0a) 20:20:20 15:15:30 Humic acid + 15:15:30 12:12:36 + 12:12:44 (liquid) 40:0:0 20:20:20 Ca-containing fertilizer 10:17:27 10:12:36
1 week after transplanting 1 month later 1 month later Later At harvesting From transplanting till ripening From transplanting till ripening From transplanting till ripening At ripening Last 2 weeks
2 2 2 1 2 3 3 3 3 3
Pepper
a) N:P:K.
kg per greenhouse (GH), once a week for 4 weeks kg per GH, once a week for 4 weeks kg per GH, once a week for 8 weeks L + 1 kg per GH, once a week for 1 month kg + 1 L per GH, once a week till end of season kg per GH, 4 times every 2 weeks kg per GH, once every 4 d for 1 month kg per GH, twice a month kg per GH, once every 4 d for 1 month kg per GH, once every 4 d
PRODUCTION SYSTEM IMPACT ON SOIL QUALITY
and 8.2, respectively, for the pepper and tomato greenhouses, whereas the uncultivated soil had an average pH value of 8.1 in the topsoil (Fig. 1). Almost similar pH values were found in the subsoil layer. In contrast to soil pH, there were greater variations among the EC values (Fig. 1). The EC values in the topsoil were 3.01 and 2.97 dS m−1 for the tomato and pepper greenhouses, respectively, compared to 1.18 dS m−1 in the uncultivated soil. Salt accumulation was also observed in the subsoil where the tomato and pepper greenhouses had EC values of 2.04 and 2.61 dS m−1 , respectively, compared to 0.71 dS m−1 in the uncultivated soil. Soil TN and NO3 -N The contents of TN and NO3 -N in the intensively managed greenhouses and uncultivated soil in both soil layers are shown in Fig. 2. TN in the topsoil ranged from 0.6 to 1 g kg−1 , however, the subsoil of pepper greenhouses had 1.6 g kg−1 TN compared to 0.4 and 0.9 g kg−1 , respectively, for the tomato greenhouses and uncultivated soil (Fig. 2). In the current study, IGPS resulted in significantly higher residual NO3 -N contents for both soil layers compared to the uncultivated soil, particularly in the case of tomato greenhouses (Fig. 2). The residual soil NO3 -N after harvest was approximately 7.4, 4.1 and 2.5 mg kg−1 , respec-
285
tively, for the tomato greenhouses, pepper greenhouses and uncultivated soil in the topsoil layer (Fig. 2). Soil NO3 -N also accumulated in the subsoil layer (4.7, 3.5, and 1.3 mg kg−1 , respectively, for the tomato greenhouses, pepper greenhouses and uncultivated soil). Soil Olsen-P There was significantly higher Olsen-P content in the greenhouse soils than in the uncultivated soil in both soil layers (Fig. 3). In the uncultivated soil, OlsenP content was 39.1 and 22.8 mg kg−1 , respectively, for the top- and subsoils. In the tomato greenhouses, it was 135.2 and 81.3 mg kg−1 for the top- and subsoils, while in the pepper greenhouses the corresponding values were 139.4 and 84.8 mg kg−1 , respectively. Available K, soluble Ca and Mg, and OM The values of soil fertility indicators such as available K (soluble and exchangeable K) in the topsoil layer of greenhouses were significantly lower than those in the uncultivated soil (Fig. 4). IGPS, particularly in the case of pepper, led to a significant increase (P < 0.05) in Ca content in both soil layers for both crops compared to that in the uncultivated soil (Fig. 4). IGPS also led to a significant increase (P < 0.05) in the Mg content for both crops compared to that in the uncultivated soil for both soil layers (Fig. 4).
Fig. 1 Soil pH and electrical conductivity (EC), with the extract ratio of 1:1 soil:water, in the top- (0–20 cm) and subsoil (20–40 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 18, 20, and 4, respectively, for tomato, pepper, and control).
286
T. G. AMMARI et al.
Fig. 2 Total N and NO3 -N in the top- (0–20 cm) and subsoil (20–40 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter(s) are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 18, 20, and 4, respectively, for tomato, pepper, and control).
Fig. 3 Olsen-P in the top- (0–20 cm) and subsoil (20–40 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 18, 20, and 4, respectively, for tomato, pepper, and control).
Only slight accumulation of organic matter was found in the soils of greenhouses compared to the uncultivated soil (Fig. 5). Soluble Na, soluble Cl, and SO4 IGPS resulted in much higher soluble Na, soluble Cl and SO4 concentrations in the soils of greenhouses compared to those in the uncultivated soil in both soil layers (Fig. 6). Compared with the tomato greenhouse production system, intensive pepper greenhouse production system resulted in even higher Cl concentra-
tion in the subsoil and higher SO4 concentration in both soil layers. Soil biological properties IGPS had an apparent impact on soil biological properties in the topsoils (Figs. 7 and 8). Microbial counts in the uncultivated soil followed a normal trend where bacteria dominated the numbers of microorganisms followed by actinomycetes and fungi. However, IGPS resulted in a significant decrease in the bacterial count compared to the uncultivated soil (Fig. 7) and a
PRODUCTION SYSTEM IMPACT ON SOIL QUALITY
287
Fig. 4 Available K and soluble Ca and Mg in the top- (0–20 cm) and subsoil (20–40 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter(s) are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 18, 20, and 4, respectively, for tomato, pepper, and control).
Fig. 5 Organic matter in the top- (0–20 cm) and subsoil (20–40 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 18, 20, and 4, respectively, for tomato, pepper, and control).
significant increase in the fungi/bacteria ratio (f/b) (Fig. 8). In addition, the intensive tomato greenhouse production system caused an increase in the fungal as well as actinomycetes counts compared to the pepper production system and the uncultivated soil (Fig. 7). DISCUSSION Soil pH and EC The soils of the study site are highly buffered due to their high CaCO3 content (430–500 g kg−1 ). The pre-
sence of CaCO3 buffers the soils in the pH of 7.5–8.5. Thus, the long-term annual application of composted animal manure is not expected to impact soil pH of these highly calcareous soils (Fig. 1). On the other hand, IGPS, including frequent composted animal manure application, continuous fertigation without soil leaching and efficient drainage of excess salts, and high evaporation conditions, resulted in significantly higher EC for both soil layers compared to those of the uncultivated soil (Fig. 1). Salt accumulation in the topsoil of the greenhouses was due to the upward movement of
288
T. G. AMMARI et al.
Fig. 6 Soluble Na, soluble Cl and SO4 in the top- (0–20 cm) and subsoil (20–40 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 18, 20, and 4, respectively, for tomato, pepper, and control).
soil water as evapotranspiration exceeded water application (irrigation). According to Rhoades et al. (1992), the EC threshold of tomato crop is 0.9 dS m−1 and Maas and Hoffman (1977) suggested that the threshold values were 1.5 and 2.5 dS m−1 , respectively, for pepper and tomato with 14.0% and 9.9% reduction in yield per unit increase in EC beyond the threshold. Consequently, progressive salt accumulation would have adverse impact on the yield of crop, particularly for pepper. Chen et al. (2004) evaluated soil fertility in vegetable production under the open-field and greenhouse conditions including intensive fertilizer use and irrigation and reported that soil EC was 0.44 and 0.35 dS m−1 for 0–5 and 5–10 cm soil depth, respectively, for the greenhouses of 1–5 years of vegetable production and 0.56 and 0.43 dS m−1 correspondingly for the 16– 20-year greenhouses. The observed differences of the
results between the current study and those of Chen et al. (2004) are attributed to the differences in climatic conditions, crop type, soil type (e.g., texture), quality and amount of irrigation water, quantity and types of applied fertilizers, and other agricultural and/or soil management practices (e.g., type and amount of applied organic materials and excess salt leaching and drainage). Soil TN and NO3 -N Although Chen et al. (2004) showed that the values of TN in surface soil layers (pH1:5 = 7.45–8.34) were higher in the greenhouses that had been in use for a longer period of time (1.00, 1.21, 1.43, and 1.90 g kg−1 for 1–5, 5–10, 11–15, and 16–20 years of greenhouse vegetable cultivation, respectively), IGPS under the conditions of the current study did not significantly
PRODUCTION SYSTEM IMPACT ON SOIL QUALITY
Fig. 7 Average bacterial, actinomycetes and fungal counts in the topsoil (0–20 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). CFU = colony forming unit. Bars with the same letter(s) within each microbial group are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 2, 9, and 10, respectively, for control, tomato, and pepper).
Fig. 8 Fungal/bacterial (f/b) ratio in the topsoil (0–20 cm) as influenced by intensive greenhouse production systems compared to the uncultivated soil (control). Bars with the same letter are not significantly different at P ≤ 0.01 using t-test. Vertical bars indicate standard deviations of the means (n = 9, 10, and 2, respectively, for tomato, pepper, and control).
influence TN particularly in topsoil layer in comparison with the uncultivated soil (Fig. 2). Diacono and Montemurro (2010) reported that repeated application of composted materials in semi-arid Mediterranean regions enhanced soil organic N content by up to 90%. Such finding was not supported by our study. Defoer et al. (2000) reported that low values of TN were found in organic plots, which could be the result of crop uptake and N loss through volatilization. Current finding is in agreement with the latter one. Other factors might include irregular application of composted animal manure and/or poultry manure, which are rapidly decomposed leading to earlier N depletion. However, IGPS
289
of pepper crop significantly increased TN in the topsoil compared to that of tomato crop (Fig. 2). This might be attributed to the fact that farmers at the site of the current study annually applied mineral N at approximately 150 and 350 kg ha−1 , respectively, for tomato and pepper. In the subsoil layer, the TN of the uncultivated soil was even higher than that of the tomato IGPS (Fig. 2), which can be due to the growth of wild weeds with different root depths on the uncultivated soil. IGPS resulted in significantly higher residual NO3 N content for both soil layers compared to the uncultivated soil, particularly in the case of tomato greenhouses (Fig. 2). Nitrate uptake of pepper plants seemed to be much higher than that of tomato plants, which is in agreement with Yu et al. (2010), who reported that N uptake of tomato and pepper crops was 0.31 and 0.58 kg per 100 kg yield, respectively. The amounts of residual NO3 -N reported by this study (Fig. 2) are much lower than those reported in the literature. Hu et al. (2012) reported that soil residual NO3 -N after harvest was approximately 190–404 kg ha−1 at 0–60 cm soil depth in the greenhouses cultivated with vegetable crops. The differences could be attributed to the factors such as determination time of soil NO3 -N, annual N inputs from mineral fertilizers, type of N mineral fertilizer, application method of N fertilizer, timing of application, amounts of applied manures and their C:N ratios, cultivations of crops, and irrigation water in addition to the factors affecting gaseous losses of N. Several reports have shown that annual application of N to greenhouse vegetable crops has reached more than 1 000 kg ha−1 (Chen et al., 2004; Ju et al., 2009) in comparison to only 150 to 350 kg ha−1 in the current study. Moreover, the soil was graded based on its nutritional status for vegetable cultivation according to Shen and Zou (2004) and Alpaslan et al. (2005). Accordingly, residual TN as well as NO3 -N belonged to very low to medium and very low, respectively. This is in agreement with the fact that about 95% of TN in surface soils is organic N (Havlin et al., 2004). It can be concluded that TN in the soils might not be enough to support good plant growth in upcoming seasons or microbial activities and, therefore, supplementary N application is necessary under the conditions of the current study. Soil Olsen-P Significantly higher Olsen-P was found in the soils of greenhouses than in the uncultivated soil for both soil layers (Fig. 3), which can be attributed to the fact
290
that P was applied to the tomato and pepper greenhouses at high rates of approximately 234 and 192 kg P2 O5 ha−1 year−1 , respectively. The P accumulation in the IGPS may have consequently resulted from farmers’ excessive application of organic manure and compound fertilizers to obtain higher yields without any pre-plant-soil test. Previous studies have shown that long periods of greenhouse cropping caused soil available P enrichment in greenhouses (Chen et al., 2004; Yang et al., 2010), which was confirmed by our study. Chen et al. (2004) showed that available P in the soil surface layers was higher in the greenhouses used for a longer period of time (117, 158, 118, 257 mg kg−1 Olsen-P for 1–5, 5–10, 11–15, 16–20 years of greenhouse vegetable cultivation, respectively), fertilized with mineral and organic P at a rate of 410 and 565 kg ha−1 , respectively, for tomato and sweet pepper. Soil P accumulation under IGPS suggests that there is a need of better nutrient management for IGPS. In the agricultural areas with intensive farming practices, excessive application of P has led to increasing P concentrations in soils, increasing the risk of P losses by runoff, erosion and subsurface drainage water (Stanley et al., 1995). In addition, the excessive available P in soils may lead to micronutrient deficiency (e.g., Zn deficiency). According to Alpaslan et al. (2005), the residual Olsen-P in this study was classified as very high in topsoil layer and sufficient to high in subsoil layer for the tomato and pepper greenhouses. Moreover, Dobermann and Fairhurst (2000) stated that soil P in most cultivated soils was higher than the critical level of 25 mg kg−1 in calcareous soils and the differences could be explained by the application rates of fertilizer at different locations. Our results indicated that farmers at the study site did not consider soil available P status before application of additional fertilizer. Yu et al. (2010) reported that the overdose of fertilizer applied in greenhouses led the amount of available P in soil far beyond the required. In the greenhouse soils, the amount of available P was 135–377 mg kg−1 , while its required level for vegetables was only 60–90 mg kg−1 . However, soil P readily reacts with calcium ions, clay minerals and organic components in soils to form relatively insoluble substances. Similar to soil NO3 , inorganic P is also negatively charged in most soils. Dissimilarly, P does not behave like NO3 because of its reactivity with other soil constituents. Available K, soluble Ca and Mg, and OM Available K in all soil samples including the uncultivated soil was classified as high to very high in
T. G. AMMARI et al.
both soil layers according to Alpaslan et al. (2005), although available K in the topsoil under IGPS was lower than that in the uncultivated soil (Fig. 4). The results of this study are higher than those reported in the literature. Yu et al. (2010) reported available K in greenhouse soils of 192 to 764 mg kg−1 . Similarly, Chen et al. (2004) reported available K in greenhouse soils of 67 to 753 mg kg−1 and that tomato and sweet pepper were fertilized with mineral and organic K at a rate of 232 and 283 kg ha−1 , respectively. In the current study, tomato and pepper were fertilized with mineral K at a rate of approximately 240 kg ha−1 . Similar to P, farmers at the study site should also consider the residual available K in soils when applying K fertilizers to succeeding crops. Intensive greenhouse production led to a significant increase in Ca in top- and subsoils for both crops, particularly in the case of pepper. Significant increase in Mg content was also found in both soil layers for both crops compared to that in the uncultivated soil (Fig. 4). The observed increases in Ca and Mg can be partially attributed to greater dissolution of CaCO3 /MgCO3 due to higher partial pressure of carbon dioxide (PCO2 ) in the cultivated soils. In the subsoil, significantly higher Ca and Mg contents in the case of pepper might be attributed to the differences in root architecture (e.g., root depth) and consequently PCO2 of subsoil. No considerable accumulation of organic matter (OM) was found in the soils of greenhouses compared to the uncultivated soil (Fig. 5), which can be attributed to the fact that the temperature of greenhouses is much higher and the activity of microorganisms is stronger resulting in rapid mineralization of applied organic materials (Yu et al., 2010). Coskan et al. (2012) also reported that about 30% and 50% of the surveyed greenhouses had soil OM content of 10– 20 and 20–30 g kg−1 , respectively. Soluble Na, soluble Cl, and SO4 Intensive greenhouse production led to significant accumulation of Na, Cl, and SO4 in both soil layers, particularly in the case of pepper (Fig. 6). Because Cl is usually supplied to plants from various sources, particularly from irrigation water (maximum concentrations of total dissolved solids, Cl, and Na in the water of the King Talal Reservoir were 2 595, 532.5, and 345 mg L−1 , respectively) (Ammari et al., 2013), there is much more concern about its toxic levels in plants than deficiency. The Cl concentration in the external solutions of more than 710 mg L−1 can lead to Cl toxicity in sensitive plant species (Marschner, 1986). High Cl concentrations might have more detrimental effect on
PRODUCTION SYSTEM IMPACT ON SOIL QUALITY
pepper than on tomato plants, which can withstand Cl concentration up to approximately 1 380 mg L−1 . In the semiarid and arid regions, the Na concentration of approximately 1 150 to 2 300 mg L−1 is typical under irrigation and have a rather detrimental effect on the growth of most crop plants (Marschner, 1986). Although accumulation of soluble Na was found under the conditions of IGPS compared to the uncultivated soil, Na concentration was far below that reported by Marschner (1986). The SO4 concentration of 3 to 5 mg L−1 in solution is sufficient for most crops (Havlin et al., 2004). Large seasonal and year-to-year fluctuations in SO4 can occur due to the influence of environmental conditions on organic S mineralization, downward or upward movement of SO4 in soil water, and SO4 uptake by plants. The SO4 content in soils is also affected by the application of S-containing fertilizers and irrigation water. High concentrations of Cl and SO4 might affect soil quality. Therefore, leaching and drainage practices should be reconsidered for intensive greenhouse production practices. Soil biological properties Agricultural practices such as cropping index (i.e., percentage of the number of crops grown on a given land area per year), irrigation and water quality, type, timing and rate of fertilizers, and plant protection measures at the study site had adverse effects on soil EC, Na, Cl, SO4 , and NO3 contents, which might explain the variations in soil biological properties (i.e., bacterial counts and fungi:bacteria ratio) in comparison with those of the uncultivated soil (Figs. 7 and 8). In the case of tomato greenhouse production system, the observed significant increase in fungal counts, compared to those of pepper greenhouse production system and uncultivated soil (Fig. 7), might be an indication of the quality of soil OM, i.e., an increase in lignin and humus fractions. Fungal growth increases when the lignin fraction of soil OM increases since fungi are more adapted to lignin decomposition compared with bacteria. Sources of plant nutrients (synthetically derived minerals vs. decomposed organic material) have larger effect on microbial communities than land management systems (organic, low-input, or conventional) (Bossio et al., 1998). A different soil microbial community was reported by long-term organic fertilization experiments (Toyota and Kuninaga, 2006; Chu et al., 2007; Espersch¨ utz et al., 2007). Such variations of soil biological properties result from the nature of the added organic amendment, where complex compounds favor the growth of fungi and actinomycetes, and partly, because of the addition of the manure-
291
associated microorganisms in large numbers (Green et al., 2007). Espersch¨ utz et al. (2007) reported low f/b values of 0.017 and 0.024 for mineral and organic fertilizer amendments, respectively. Generally, the f/b ratio increased with higher amount of fertilizer added, suggesting that enhanced nutrient availability supported fungal growth. However, this contradicts other studies reporting high soil fertility and nutrient availability to favor bacteria over fungi (Grayston et al., 2001). It is likely that the changes in microbial communities cannot be solely attributed to quantitative differences in resource supply. Besides fertilizer regime, the identity of crop species also influenced microorganisms (i.e., actinomycetes counts under tomato and pepper intensive greenhouse systems) as shown in Fig. 7 and as found by Ngosong et al. (2010). The disproportionate response of microorganisms could be derived from plant specific differences in rhizo-deposition or root architecture since they can affect the ratio of microbial carbon to organic carbon (Anderson and Domsch, 1989; Insam et al., 1989). Overall, the impact of crop type on soil microorganisms was more pronounced than long-term fertilizer practice. This underlines the fact that root exudation and root morphology actively shaped soil microbial communities (Berg and Smalla, 2009). Moreover, management practices like the timing of fertilizer and manure applications can interact with crop biological factors, i.e., root architecture and exudates. Thus, the observed response of microorganisms to both crops (Fig. 7) was basically an overall effect of all factors linked with crops. This is essential for the achievement of sustainable agriculture and soil conservation, since crop rotation does not only affect the related plant symbionts but also selects the associated microorganisms, which in turn fulfill important functions for plant growth, soil health and quality (Wu et al., 2008). CONCLUSIONS The IGPS with excess fertigation but poor drainage under high evaporation conditions resulted in higher EC in top- and subsoils compared to the uncultivated soil. Progressive salt accumulation was expected to have adverse impact on yield of particularly pepper. IGPS under the conditions of this study also resulted in low soil N. Low TN was probably due to crop uptake, loss through volatilization and irregular application of composted animal manure or poultry manure. Much higher Olsen-P contents in the soils of greenhouses, compared to that in the uncultivated soil, were due
292
to the excessive application of animal manure, mineral P and compound fertilizers to obtain high yields. The Olsen-P was categorized as very high in the topsoil layer and sufficient to high in the subsoil layer, which poses environment risks. Available K in the topsoil layer of greenhouses was relatively lower than that in the uncultivated soil. However, the available K in all soil samples including the uncultivated soil was considered to be high to very high in both soil layers. IGPS did not influence soil OM content but increased Na, Cl and SO4 concentrations in both soil layers compared to the uncultivated soil. Progressive Cl accumulation is expected to have adverse effect on yield of particularly pepper crop. IGPS caused a considerable decrease in the bacterial count compared to the uncultivated soil. Although not significant, the intensive tomato greenhouse production system caused an increase in the fungal and actinomycetes counts compared to both pepper IGPS and uncultivated soil. It can be concluded that not only the intensive production practices but also crop types had an impact on soil biological properties. Current findings suggest that sustainable and profitable soil management practices should be adopted by farmers in the central Jordan Valley through targeted extension programs to educate farmers on the best management practices. ACKNOWLEDGEMENT Authors would like to thank the Jordan Valley Authority for their technical and laboratory assistance. REFERENCES Alpaslan, M., Gunes, A. and Inal, A. 2005. Research Techniques. AU Agriculture Faculty Publish, Ankara. Al-Zu’bi, Y. and Al-Kharabsheh, A. 2003. Multicriteria analysis for water productivity in the Jordan Valley. Int. Water Resour. As. 28: 501–511. Ammari, T. G., Tahhan, R., Abubaker, S., Al-Zu’bi, Y., Tahboub, T., Ta’any, R., Abu-Romman, S., Al-Manaseer, N. and Stietiya, M. H. 2013. Soil salinity changes in the Jordan Valley potentially threaten sustainable irrigated agriculture. Pedosphere. 23: 376–384. Anderson, T. H. and Domsch, K. H. 1989. Ratios of microbial biomass carbon to total organic carbon in arable soils. Soil Biol. Biochem. 21: 471–479. Berg, G. and Smalla, K. 2009. Plant species and soil type cooperatively shape the structure and function of the microbial communities in the rhizosphere. FEMS Microbiol. Ecol. 68: 1–13. Bossio, D. A., Scow, K. M., Gunapala, N. and Graham, K. J. 1998. Determinants of soil microbial communities: Effects of agricultural management, season, and soil type on phospholipids fatty acid profiles. Microbial Ecol. 36: 1–12. Chen, Q., Zhang, X. S., Zhang, H. Y., Christie, P., Li, X. L., Horlacker, D. and Liebig, H. P. 2004. Evaluation of current
T. G. AMMARI et al.
fertilizer practice and soil fertility in vegetable production in the Beijing region. Nutr. Cycl. Agroecosys. 69: 51–58. Chu, H. Y., Lin, X. G., Fujii, T., Morimoto, S., Yagi, K., Hu, J. L. and Zhang, J. B. 2007. Soil microbial biomass, dehydrogenase activity, bacterial community structure in response to long-term fertilizer management. Soil Biol. Biochem. 39: 2971–2976. Coskan, A., Atilgan, A., Oz, H. and Isler, E. 2012. Instantaneous evaluation of nitrate, ammonium, phosphorus and potassium pools in greenhouse soils in Antalya Province of Turkey. Afr. J. Agr. Res. 7: 937–942. Defoer, T., Budelman, A., Toulmin, C. and Carter, S. E. 2000. Building common knowledge: Participatory learning and action research (Part 1). In Defoer, T. and Budelman, A. (eds.) Managing Soil Fertility in the Tropics. A Resource Guide for Participatory Learning and Action Research. Royal Tropical Institute, Amsterdam. pp. 165–166. Diacono, M. and Montemurro, F. 2010. Long-term effects of organic amendments on soil fertility. A review. Agron. Sust. Dev. 30: 401–422. Dobermann, A. and Fairhurst, T. H. 2000. Rice: Nutrient Disorders and Nutrient Management. Potash & Phosphate Institute, Potash & Phosphate Institute of Canada, and International Rice Research Institute, Singapore, Makati. Doran, J. W. and Parkin, T. B. 1994. Defining and assessing soil quality. In Doran, J. W., Coleman, D. C., Bezdicek, D. F. and Stewart, B. A. (eds.) Defining Soil Quality for a Sustainable Environment. SSSA Special Publication No. 35. Soil Science Society of America and American Society of Argonomy, Madison, WI. pp. 3–21. Espersch¨ utz, J., Gattinger, A., M¨ ader, P., Schloter, M. and Fließbach, A. 2007. Response of soil microbial biomass and community structures to conventional and organic farming systems under identical crop rotations. FEMS Microbiol. Ecol. 61: 26–37. Food and Agriculture Organization (FAO). 1993. The State of Food and Agriculture 1993. FAO, Rome. Gim´ enez, C., D´ıaz, E., Rosado, F., Garc´ıa-Ferrer, A., S´ anchez, M., Parra, M. A., D´ıaz, M. and Pe˜ na, P. 2001. Characterization of current management practices with high risk of nitrate contamination in agricultural areas of southern Spain. Acta Hortic. 563: 73–80. Grayston, S. J., Griffith, G. S., Mawdsley, J. L., Campbell, C. D. and Bardgett, R. D. 2001. Accounting for variability in soil microbial communities of temperate upland grassland ecosystems. Soil Biol. Biochem. 33: 533–551. Green, S. J., Michel Jr., F. C., Hadar, Y. and Minz, D. 2007. Contrasting patterns of seed and root colonization by bacteria from the genus Chryseobacterium and from the family Oxalobacteraceae. ISME J. 1: 291–299. Harris, R. F. and Bezdicek, D. F. 1994. Descriptive aspects of soil quality/health. In Doran, J. W., Coleman, D. C., Bezdicek, D. F. and Stewart, B. A. (eds.) Defining Soil Quality for a Sustainable Environment. SSSA Special Publication No. 35. Soil Science Society of America and American Society of Argonomy, Madison, WI. pp. 23–35. Havlin, J. L., Tisdale, S. L., Nelson, W. L. and Beaton, J. D. 2004. Soil Fertility and Fertilizers: An Introduction to Nutrient Management. 7th Edition. Pearson Prentice Hall, Upper Saddle River, NJ. Hu, Y. C., Song, Z. W., Lu, W. L., Poschenrieder, C. and Schmidhalter, U. 2012. Current soil nutrient status of intensively managed greenhouses. Pedosphere. 22: 825–833. Insam, H., Parkinson, D. and Domsch, K. H. 1989. Influence of macroclimate on soil microbial biomass. Soil Biol. Biochem.
PRODUCTION SYSTEM IMPACT ON SOIL QUALITY
21: 211–221. Ju, X. T., Xing, G. X., Chen, X. P., Zhang, S. L., Zhang, L. J., Liu, X. J., Cui, Z. L., Yin, B., Christie, P., Zhu, Z. L. and Zhang, F. S. 2009. Reducing environmental risk by improving N management in intensive Chinese agricultural systems. P. Natl. Acad. Sci. USA. 106: 3041–3046. Maas, E. V. and Hoffman, G. J. 1977. Crop salt tolerance— current assessment. J. Irr. Drain. Div. 103: 115–134. Marschner, H. 1986. Mineral Nutrition of Higher Plants. Academic Press, London. Ngosong, C., Jarosch, M., Raupp, J., Neumann, E. and Ruess, L. 2010. The impact of farming practice on soil microorganisms and arbuscular mycorrhizal fungi: Crop type versus long-term mineral and organic fertilization. Appl. Soil Ecol. 46: 134–142. Rhoades, J. D., Kandiah, A. and Mashali, A. M. 1992. The Use of Saline Waters for Crop Production. Irrigation and Drainage Paper No. 48. FAO, Rome. Ryan, J., Estefan, G. and Rashid, A. 2001. Soil and Plant Analysis Laboratory Manual. 2nd Edition. The International Center for Agricultural Research in the Dry Areas (ICARDA) and the National Agricultural Research Center (NARC), Aleppo, Syria. Shen, H. and Zou, G. Y. 2004. Parameters selection for evaluation of vegetable soil quality and its gradation. Chin. J. Soil Sci. (in Chinese). 35: 553–557.
293
Stanley, C. D., McNeal, B. L., Gilreath, P. R., Creighton, J. F., Graham, W. D. and Alverio, G. 1995. Nutrient-loss trends for vegetable and citrus fields in west-central Florida: II. Phosphate. J. Environ. Qual. 24: 101–106. Toyota, K. and Kuninaga, S. 2006. Comparison of soil microbial community between soils amended with or without farmyard manure. Appl. Soil Ecol. 33: 39–48. Weinbaum, S. A., Scott Johnson, R. and DeJong, T. M. 1992. Causes and consequences of overfertilization in orchards. HortTechnology. 2: 112–121. Wu, T., Chellemi, D. O., Graham, J. H., Martin, K. J. and Rosskopf, E. N. 2008. Comparison of soil bacterial communities under diverse agricultural land management and crop production practices. Microbial Ecol. 55: 293–310. Yang, L. J., Li, T. L., Li, F. S. and Lemcoff, J. H. 2010. Longterm fertilization effect on fraction and distribution of soil phosphorus in a plastic-film house in China. Commun. Soil Sci. Plan. 42: 1–12. Yu, H. Y., Li, T. X. and Zhang, X. Z. 2010. Nutrient budget and soil nutrient status in greenhouse system. Agr. Sci. China. 9: 871–879. Zuberer, D. A. 1994. Recovery and enumeration of viable bacteria. In Weaver, R. W., Angle, J. S. and Bottomley, P. S. (eds.) Methods of Soil Analysis. Part 2. Microbiological and Biochemical Properties. Soil Science Society of America, Madison, WI. pp. 119–144.